1. Field of the Invention
The invention relates to a filtering device for individually treating a plurality of channels in a television signal cable distribution system, comprising a plurality of parallel paths each provided with a bandpass filter having a central frequency which is controlled by a voltage applied to a frequency control input.
The invention also relates to a collective television signal distribution system.
2. Description of Related Art
Filtering devices as described in the opening paragraph are marketed by several manufacturers. The most sophisticated devices comprise filters having frequencies which are determined by variable capacitance diodes set one by one for each filter during manufacture, while the control voltage values of these variable capacitance diodes are stored for each variable capacitance diode and for each frequency. The installation is thus easy because it is sufficient for an engineer to recall a stored value for obtaining the desired control. Nevertheless, when the system ages, the necessary voltages are susceptible of varying with time, and the system gets out of order.